Studies have shown that maximum loads are important in the development of skeletal muscle and increase of bone mineral density. In 2004, the Surgeon General's Report on Bone Health and Osteoporosis (See, Chapter 9) stated: “Increases in bone mineral density, to prevent or reverse the effects of osteoporosis, are stimulated by maximum loading on the musculoskeletal system.” Zatsiorsky and Kraemer, in their 2006 book, Science and Practice of Strength Training (P. 50), explained the difference between the two different types of muscular growth: “sarcoplasmic hypertrophy of muscle fibers is characterized by the growth of sarcoplasm (semifluid interfibrillar substance) and non-contractile proteins that do not directly contribute to the production of muscle force.” Stated differently, sarcoplasmic hypertrophy happens when an individual engages in physical movement with load applied.
Conventional exercise or fitness apparatuses, however, provide only fixed or moderated resistance to users. This resistive force is typically derived from the force of gravity acting on one or more masses, or in some cases a hydraulic cylinder where viscous forces restrict the travel of a movable element within the cylinder. In such devices the amount of load applied over the range of motion of the applicable muscle groups worked by the exercise is set prior to the initiation of the exercise. Moreover, because resistance magnitude is determined prior to the performance of the exercise, the only feedback provided to the users by that endeavor is only binary. They are either able to complete the exercise, or find that it is too difficult to perform. In the case of success with the exercise, the user learns that their weakest point in the range of muscle group motion associated with the exercise provides the requisite force needed to satisfy the selected difficulty setting. In the case of failure with the exercise, the user learns that their weakest point in the range of muscle group motion associated with the exercise fails to provide the requisite force needed to the achieve the selected difficulty setting.
Neither of these outcomes reveals the actual maximum amount of force the user may exert for that exercise in their weakest point in the range of muscle group motion associated with the exercise, or, for that matter, the amount of force they could exert at any other point in the range of motion associated with the exercise. Because muscles fatigue in response to high loads, it is not feasible to ascertain one's maximum capacity in one's weakest range of motion by starting with a small load and repeating the exercise at ever increasing loads. After several trials, the fatigued muscle is unable to approach its previous maximum load.
Furthermore, conventional exercise or fitness apparatuses do not provide users with actual loading information, in particular, the maximum force exertion at any point in the range of user motion associated with a particular exercise.
Thus, what are needed in the art are devices that can permit exercisers to exert high load (e.g., force) or highest possible load in any one of a plurality of positions throughout the entire range of user motion associated with an exercise apparatus without first passing through a weak point in the range of motion, and can provide exercisers with actual loading information on such exercises.